Immobilization of laccase on itaconic acid grafted and Cu(II) ion chelated chitosan membrane for bioremediation of hazardous materials

BACKGROUND: Chitosan membranes were formed through a phase inversion technique and then cross‐linked with epichlorohydrin (CHX). Heterogeneous graft copolymerization of itaconic acid (IA) onto membrane was carried out with different monomer concentrations (CHX‐g‐p(IA)). The membrane properties such as equilibrium swelling ratio, porosity, and contact angle were measured, together with analysis by scanning electron microscopy (SEM), energy dispersive analysis of X‐rays (EDAX), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy. RESULTS: The Cu(II) ion incorporated membranes (i.e. CHX‐g‐p(IA)‐Cu(II)) were used for reversible immobilization of laccase using CHX‐g‐p(IA) membrane as a control system. Maximum laccase adsorption capacities of the CHX‐g‐p(IA) and CHX‐g‐p(IA)‐Cu(II) membranes (with 9.7% grafting yield) were found to be 6.3 and 17.6 mg mL^?1 membrane at pH 4.0 and 6.0, respectively. The K_m value for immobilized laccase on CHX‐g‐p(IA)‐Cu(II) (4.16 × 10^?2 mmol L^?1) was 2.11‐fold higher than that of free enzyme (1.97 × 10^?2 mmol L^?1). Finally, the immobilized laccase was used in a batch system for degradation of three different dyes (Reactive Black 5, RB5; Cibacron Blue F3GA, CB; and Methyl Orange, MO). The immobilized laccase on CHX‐g‐p(IA)‐Cu(II) membrane was more effective for removal of MO dye than removal of CB and RB5 dyes. CONCLUSION: Flexibility of the enzyme immobilized grafted polymer chains is expected to provide easy reaction conditions without diffusion limitation for substrate dye molecules and their products. The support described, prepared from green chemicals, can be used for the immobilization of industrially important enzymes. Copyright © 2012 Society of Chemical Industry     

Polymeric Materials: Patterned Polymer Carpets (Small 5/2011)

For the development of polymer carpets as active devices for micro‐ and nanotechnology, a control of the polymer carpet morphology and especially control of the stimulus responsive polymer brush is needed. Here, we report on the first example for the fabrication of patterned polymer carpets. On a two‐dimensional framework of fully crosslinked and chemically patterned nanosheets, polymer brushes of styrene and 4‐vinyl pyridine were grafted by self‐initiated surface photopolymerization and photografting (SIPGP). It was found that polymer grafting by SIPGP occurred over the entire nanosheets but with a preferred grafting on the amino functionalized nanosheet areas. This results in continuous polymer carpets with an intact nanosheet framework but with amplification of the chemical patterning into a three dimensional topography of the grafted polymer brush. In the case of negative patterned nanosheets, the patterned carpet could be prepared as freestanding ultrathin membranes. Furthermore, swelling experiments with poly(4‐vinyl pyridine) carpets showed that the patterns induces a directional buckling of the flexible polymer carpet. This may open the possibility of the development of micro‐ or nanoactuator devices with anisotropic responds upon environmental changes.     

The effect of plasma electrolytic oxidation process parameters on the tribocorrosion properties of TiO2 coatings

Despite the fact that Titanium and its alloys are materials which have excellent corrosion-resistant properties, they have poor wear and friction performance under tribological conditions. The aim of this study is to find suitable parameters for the surface treatment of Cp-Ti substrates which are used under saline environment. In this study, TiO₂ coatings were grown on Cp-Ti substrates at different frequencies which are parameters of the coating process. Due to its low cost and ability to achieve high thicknesses, The Plasma Electrolytic Oxidation (PEO) method was applied to grow TiO₂ coatings. The microstructures, morphology, and crystallographic structure were analyzed using SEM and XRD. Tribocorrosion properties of the coatings were investigated using a combination of the pin-on-disk wear test and potentiodynamic polarization test units. The frequency is known to have a strong impact on the PEO process. The impacts of frequency changes on the PEO coating performance were examined under a constant voltage. As result, the increase of the frequency caused smaller pores and cracks in the surface morphology of the coating and at the same time this yielded an increment on the tribocorrosion behavior of the coating.     

The effect of cryogenic treatment on tapping

This study was realized with two different types (flat and thread rolled) of coated (TiAlN), uncoated, and cryogenically treated taps (uncoated). The tapping processes were carried at four different cutting speeds (2, 3, 4, and 5 m/min) and 1.25 mm/rev feed rate under dry and wet cutting conditions on the Ti-6Al-4 V alloy. The measured cutting forces (cutting torque) were evaluated according to the cutting tool and cutting parameters. The best results in terms of cutting torque were obtained with straight flutes with spiral point taps. For the coated cutting tools, it was seen that the cutting torque was higher with respect to the other tools. The cutting fluid caused decreases in cutting forces for both of the cutters. Under dry cutting conditions, in the cryogenically treated tool, cutting torques came out to be lower with respect to the coated and uncoated tool.     

Three‐dimensional printed wideband,dual‐cavity Ku‐band antenna

A novel three‐dimensional (3D) printed, wideband, and low cost bull's eye antenna is proposed and designed for Ku‐band applications. The proposed antenna covers entire Ku‐band satellite communication bands starting from 10.5 GHz to 14.5 GHz. The antenna structure consists of dual‐cavity radiating aperture surrounded by a circular groove. With the addition of cavity and corrugation, the antenna gain is increased more than 6 dB. The antenna is fabricated using 3D printing technology and conductive painting. Measurement results indicate that the antenna has 72% fractional bandwidth from 8 GHz to 17 GHz. Measured antenna peak gain is 13.5 dBi at 13 GHz and no less than 11.5 dBi throughout the entire Ku band.     

FLUKA Simulations of DPA in 6H–SiC Reactor Blanket Material Induced by Different Radiation Fields Frequently Mentioned in Literature

Silicon carbide (SiC) is used extensively for the production of high-tech semiconductor devices. Today the use of this material in radiation environments such as fusion reactors creates excitement in the nuclear industry. Specific radiation types and energies which semiconductors were frequently exposed are of great value in terms of high-tech device studies. We used FLUKA simulation code to investigate radiation induced effects in 6H–SiC for different energetic protons, neutrons, photons and electrons in this paper. We analyzed displacement per atom values taking account of the simulation results in a very large perspective of radiation type and energy.     

Recursive Approximation of Complex Behaviours With IoT-Data Imperfections

This paper presents an approach to recursively estimate the simplest linear model that approximates the time-varying local behaviors from imperfect(noisy and incomplete) measurements in the internet of things(IoT) based distributed decision-making problems. We first show that the problem of finding the lowest order model for a multi-input single-output system is a cardinality(l0) optimization problem, known to be NP-hard.To solve the problem a simpler approach is proposed which uses the recently developed atomic norm concept and the modified Frank-Wolfe(mFW) algorithm is introduced. Further, the paper computes the minimum data-rate required for computing the models with imperfect measurements. The proposed approach is illustrated on a building heating, ventilation, and air-conditioning(HVAC) control system that aims at optimizing energy consumption in commercial buildings using IoT devices in a distributed manner. The HVAC control application requires recursive thermal dynamical model updates due to frequently changing conditions and non-linear dynamics. We show that the method proposed in this paper can approximate such complex dynamics on single-board computers interfaced to sensors using unreliable communication channels. Real-time experiments on HVAC systems and simulation studies are used to illustrate the proposed method.     

The Effect of Calcined Colemanite Addition on the Mechanical Strength of Magnetite Pellets Produced with Organic Binders

Iron ore pellets must have sufficient mechanical strengths against degradation in all stages of pellet production. Low strength is also a problem for product pellets since they abrade during transportation to the reduction furnaces. The use of a binder is necessary to provide sufficient strength to the pellets and for better operation and handling of pellets. Bentonite is the standard binder in the industry; however, it is considered an impurity due to its acid oxide contents. Organic binders have been tested for many years as alternative binder to bentonite. They have been found to give sufficient wet pellet properties. However, they failed to provide sufficient strength to the preheated and fired pellets due to lack of slag bonding. It has been assumed that one possible effective method to improve the preheated and fired pellet strengths is addition of a slag-bonding constituent. In this study, calcined colemanite was added to the pellet feed to overcome the lower strength problem encountered with organic binder use. The strength of pellets produced with organic binders and calcined colemanite alone and in combination was comparatively studied against the strength of pellets made with standard bentonite binder in magnetite concentrate pelletizing. The results showed that addition of calcined colemanite into the pellet mixture improved the preheated and fired pellet strengths of pellets produced with organic binders.     

A dynamometer design and its construction for milling operation

In this study, a strain gauge based dynamometer capable of measuring three-force components during metal cutting has been designed and constructed. In order to read and save the cutting force data automatically on a computer during metal cutting, a data acquisition system with the necessary hardware and software was also devised and connected to the developed dynamometer. Cutting force signals were captured and processed using a personal computer through operational amplifiers and analog-to-digital converter. Although the dynamometer was developed primarily for milling operations, it can be used to measure cutting forces during nearly all machining operations (turning, grinding, drilling, etc.). Machining tests were performed at different cutting parameters and the results showed that the dynamometer could be used reliably to measure cutting forces.